A highly stereoselective Michael addition of alpha-amino acid-derived 2-benzyloxythiazol-5(4H)-ones to dimethyl allenedicarboxylate was developed by employing P-spiro chiral triamino-iminophosphorane bearing (S)-sec-butyl groups as a catalyst. Theoretical investigation of the transition-state models for the reaction and control experiments suggested the intervention of a dynamic kinetic resolution of the axially chiral allene acceptor. The synthetic utility of this method was demonstrated through the transformation of the stereochemically homogeneous Michael adduct to an alpha-vinylic alpha-amino acid derivative.